Scientists study 500-year dry spell in the Sierra Nevada

Scientists have found evidence in Sequoia National Park of a centuries-long dry spell -- and clues about how the Sierra Nevada could be changing.

The researchers studied tree rings on dead giant sequoias, the largest trees on Earth. They found that during a warm, dry period between A.D. 800 and 1300, fires were more frequent, suggesting more fires may be ahead for a Sierra facing similar conditions today.

Their findings have been published in the most recent edition of the journal "Fire Ecology," said Thomas W. Swetnam, lead researcher and director of the Tree Ring Laboratory at the University of Arizona in Tucson. Information about how sequoias responded to the 500-year warm spell is important because scientists predict climate change may subject the forest to a similar environment again, Swetnam said.